Refactored macro mechanism

Now there is now longer a dummy DOM element corresponding to the macro
itself. Instead, macros must create a single element child. This allows
us to more easily fit Bootstrap's requirements for HTML layout (eg,
that problem with links in navbars not being recognised). The
refactoring isn't complete, there are still a few bugs to chase down

core/modules/macros/version.js

@@ -19,7 +19,7 @@ exports.info = {
 };
 
 exports.executeMacro = function() {
-	return [$tw.Tree.Text($tw.utils.getVersionString())];
+	return $tw.Tree.Text($tw.utils.getVersionString());
 };
 
 })();